Vasodilators dosage

Attempts to diminish the overall metabolism of trichloroethylene might be useful (e.g., hypothermia, mixed-function oxidase inhibitors, competitive inhibitors of trichloroethylene metabolism [i.e., P-450 substrates]), if instituted soon enough after trichloroethylene exposure. Catecholamines (especially beta agonists) act in concert with trichloroethylene, increasing the risk of cardiac arrhythmias. Hence, catecholamines should be administered to patients only in the lowest efficacious doses and for certain limited presentations of trichloroethylene poisoning. Ethanol should also be avoided because concurrent exposure to trichloroethylene and ethanol can cause vasodilation and malaise and may potentiate central nervous system depression at high dosage levels of either compound. 

Advise patients that initiation of treatment and (to a lesser extent) dosage increases may be associated with transient symptoms of dizziness or lightheadedness (and rarely syncope) within the first hour after dosing. Thus, during these periods, avoid situations such as driving or hazardous tasks, where symptoms could result in injury. In addition, vasodilatory symptoms often do not require treatment, but it may be useful to separate the time of dosing of carvedilol from that of the ACE inhibitor or to temporarily reduce the dose of the ACE inhibitor. Do not increase the dose of carvedilol until symptoms of worsening heart failure or vasodilation have been established. 

Sodium nitroprusside (SNP) is both a venous and an arterial vasodilator. An important part of its vasodilator action is caused by the release of nitric oxide (NO), similarly as for the organic nitrates. SNP can only be administered via the intravenous route. It is a rapidly and short acting vasodilator. It has been used in the treatment of hypertensive emergencies and in the management of myocardial ischaemia. In spite of its vasodilator action it hardly influences heart rate, in contrast to hydralazine and minoxidil. The dosage of SNP should not be higher than 3 pg/kg/min within 48 h, in order to avoid the rise of cyanide ions and thiocyanate in the blood. 

Anesthesia of the mucous membranes of the ear. nose, and throat is usually brought about by use of aqueous solutions of the. salts of tetracaine, lignocainc. or cocaine. The vasodilator effect of cocaine reduces bleeding in surgical procedures. However, all local ane.sthetics are rapidly absorbed through mucoas membranes, and so their ase may be accompanied by an increa.scd risk of toxic. systemic reactions. As a result, dosage must be carefully controlled. 

Williams SG, Cooke GA, Wright DJ, Tan LB. Disparate results of ACE inhibitor dosage on exercise capacity in heart failure a reappraisal of vasodilator therapy and study design. Int J Cardiol 2001 77 239-45. 

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